fix(a11y): bump all text below 12px to 12px floor and promote tertiary-on-body to secondary

Brand guidelines (docs/brand/magnotia-brand-guidelines.md §4) say "Never go
below 12px for any text" and "tertiary text must be ≥18px bold or ≥24px
regular". Audit found 246 sub-12px className sites and 166 cases of
text-text-tertiary paired with body sizes.

Bumped text-[9/10/11px] → text-[12px] across 26 .svelte files in src/lib
and src/routes. Promoted text-text-tertiary → text-text-secondary at body
sizes (12-14px) where context allowed; left placeholder pseudo-states,
ternary-conditional inactive states, and line-through "done" states alone
(8 residual pairings, all decorative).

Affects neurodivergent users on 1366×768 budget hardware most directly.
svelte-check: 0 errors, 0 warnings.

src/lib/components/HotkeyRecorder.svelte

@@ -198,19 +198,19 @@
   >
     <span class="sr-only" aria-live="polite">{srStatus}</span>
     {#if recording}
-      <span class="text-[11px] text-text-tertiary italic">Hold Ctrl/Alt/Super + key. Esc to cancel.</span>
+      <span class="text-[12px] text-text-secondary italic">Hold Ctrl/Alt/Super + key. Esc to cancel.</span>
     {:else}
       {#each chips as chip, i}
         {#if i > 0}
-          <span class="text-[10px] text-text-tertiary" aria-hidden="true">+</span>
+          <span class="text-[12px] text-text-secondary" aria-hidden="true">+</span>
         {/if}
-        <span class="px-2 py-0.5 rounded-md bg-bg-elevated border border-border text-[11px] font-medium text-text
+        <span class="px-2 py-0.5 rounded-md bg-bg-elevated border border-border text-[12px] font-medium text-text
           shadow-[inset_0_1px_2px_rgba(0,0,0,0.3)]">{chip}</span>
       {/each}
     {/if}
   </button>
   {#if rejectionReason}
-    <span class="text-[11px] text-warning" role="alert">
+    <span class="text-[12px] text-warning" role="alert">
       Couldn't bind that combo. {rejectionReason}.
     </span>
   {/if}